Deep etching is basically the digital version of cutting something out like you used to do with an image from a magazine and then pasted it onto another image or plain background. You cut it out digitally in Photoshop and place that image onto something else.
This is a term which is used to describe the process of removing a specific section of an image from its background so that it stands alone. It means that you can use just that part in a different way or with a different background
While designing websites or print design this is an usual thinking that you have an image in your head of what the final product is going to look like. One problem is major this time and that is it is exceptionally rare that you find a finished photograph that has the elements you are looking for, arranged in a pleasing pattern that you will be happy to work with. Invariably, the background is cluttered or you only want to use one specific object (for example), not an entire background of them in your final design.